Days after sparking engagement rumors after being spotted with a ring on her finger at a Knicks game, Mary-Kate Olsen, 26, and her much older, much taller boyfriend, Olivier Sarkozy, 43, went out for a night on the town. They were joined by Olsen’s sister Ashley and pals at the Electric Room on Monday night. “Mary-Kate and her boyfriend were really cute and sweet and seemed really in love,” says a spy. “They were dancing together by themselves and drinking champagne.” Later they headed to No. 8 for the club’s Café Society series. The odd couple has previously shown their affection at MSG, snuggling courtside, and have been dating since last May.